Introduced Species Summary Project
Brown Trout (Salmo trutta)
Source: USGS website. Copyright Noel M. Burkhead
Common Name: Brown Trout (Other names include the German Trout, Sea Trout or Loch Leven Trout)
Scientific Name: Salmo trutta
or Division: Animalia
Identification: The brown trout is primarily a freshwater fish, but can adapt to salt water. The fish can grow to 10lbs or 102 centimeters and is noted for its fast growth rate. The brown trout’s preferred habitats are streams, lakes or brooks. The brown trout has an olive or brown colored body and dark brown or red spots. The tail is square with few or no spots on it. The ideal temperature for the brown trout is 56◦F and 66◦F. Notably, the brown trout can survive in water that may be too warm for other trout species, such as the brook trout. The trout matures in 3 to 4 years. Females spawn in the fall, producing 10,000eggs. Juvenile brown trout feed on insects or other invertebrates, but as the trout matures, they also eat other fish.
original distribution of the brown trout is documented to be
Current Distribution: Brown trout are now found
globally. Brown trout introductions have
been cited in North and
Other countries into which the
species have been introduced include
Site and Date of Introduction: Aquaculture and fish stocking are the primary means of
introduction of the brown trout to new areas.
In the mid-1800’s, brown trout aquaculture was established in
The first introduction of the brown
trout into the
Mode(s) of Introduction: According to Peter Bryant in “Biodiversity and Conservation,” the practice of aquaculture or “fish farming” is one of the leading contributors to invasive species. Bryant references Mozambique Tilapia as well as salmon farms as sources of invasive species. In addition, the diseases and viruses of these species are being introduced into new areas. As noted above, brown trout has primarily been introduced as a result of aquaculture and fish stocking. The goal of these activities was to support recreational fishing.
Reason(s) Why it has Become Established: The brown trout is able to live and grow in warmer waters than other native trout species, such as the brook trout. As such, the brown trout has been able to establish itself in many areas in which brook trout cannot exist or where warmer waters exist. Given changes temperatures and climate change, it will be interesting to understand what implications, if any, this has on the changing trout species in a given area. The brown trout also grows faster and can be bigger than native species, such as the brook trout. Therefore, in certain areas, brown trout can outcompete brook trout and other native species. The food which brown trout eat, primarily insects, mollusks and smaller fish, is also widely available and do not constrain the growth of the trout.
Brook Trout Source: US Fish and Wildlife Service. Accessed at http://www.fws.gov/midwest/IronRiver/Coaster_Brook_Trout.html; Golden Trout Source: Montana Hunting and Fishing Journal Accessed at http://www.huntingandfishingjournal.org/fishing_cold_goldentrout.php
Ecological Role: Brown trout has an ecological role in the biodiversity of rivers, lakes and streams. As brown trout play an important role in the food chains of these areas, it impacts small fish, mollusk and insect populations of its prey. Competition with other species contributes to changing fish populations, impacting the biodiversity of an area. In addition, because brown trout is adaptable to warmer water, it especially changes the biodiversity in warmer lakes and streams.
Benefit(s): The brown trout is popular with recreational
fishing communities. The ability of the brown trout to adapt to warmer areas
than brook trout and their larger size has made them popular with fisherman. Because of their growth rates, these fish are
also said to be able to withstand greater fishing pressure than other species. In
addition to aquaculture and recreational fishing, brown trout also serve as an
aquarium species. There are significant
economic benefits to trout as well. The
Because brown trout is more adaptable than brook trout, in some areas,
they are considered to outcompete native trout
species. Brown trout has been cited as reducing native species through
predation. It also displaces other
species and contributes to increased competition for food. There have been several studies that have
analyzed the impact of brown trout on other trout species, specifically the
brook and golden trout. While juvenile
brook trout can outcompete brown trout, there is
significant evidence of brown trout displacing adult brook trout as the
competition between the species changes over the lifetime of the fish.
Control Level Diagnosis: Medium. While brown trout provides benefits to recreational fisherman and economic benefits to the fishing industry overall, the impact on native species trout population and other species is considerable. Managing these populations and new introductions is an important control measure.
There are several ways in which brown trout are being controlled. One
way in which
Bryant, Peter, 2002,“Biodiversity and Conservation: A Hypertext Book” 2002.
Global Invasive Species Database, “Salmo Trutta (fish)” http://www.invasivespecies.net/database/species/ecology.asp?si=78&fr=1&sts=sss Accessed November 2006.
Illinois State Department of Natural Resources, “Illinois Exotic Species: Salmo Trutta” http://dnr.state.il.us/LANDS/EDUCATION/EXOTICSPECIES/browntrout.htm Accessed November 2006.
Integrated Taxonomic Information System website, http://www.cbif.gc.ca/pls/itisca/taxastep?king=every&p_action=containing&taxa=Salmo%20trutta. Accessed November 2006.
United States Geographical Survey, “Nonindigenous Aquatic Species: Salmo Trutta,” http://nas.er.usgs.gov/queries/collectioninfo.asp?NoCache=11%2F13%2F2006+5%3A15%3A16+PM&SpeciesID=931&State=NY&HUCNumber= Accessed November 2006.
Author: Sandra Lauterbach
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